Gen II Bent Countershaft

[Camel]

Five Hayabusa engines in the clean room, all awaiting parts.

The latest is a doozy. Bent countershaft, twisted mainshaft, bent teeth, dead dogs. Outstanding. Most smashed Hayabusa gearbox I've ever seen, (and I've seen many).

But all the gearshift forks are straight!!!! Client was changing from 2nd to 3rd whilst hard-charging when all of sudden there was a 'ka-lunk' and gears wouldn't shift. Shut it down and submitted for disassembly.

Here's the countershaft; as bent as Roger Rogerson.


The arrow to the right clearly shows twisting. The arrow to the left, brinelling from the hammering caused by the bent shaft twisting the bearing as it rotates and creating an oscillation between the two crankcase halves.

Check it out, that shaft is bent.


Braces won't fix these crooked teeth....


Dead dogs. Just about every dog had lost its edge.


I couldn't even get the gears off the mainshaft, it is seriously twisted.

Time to start scrounging for parts. Damn the see sawing Yank currency!

On a happy note, after threatening the supplier with a paypal investigation, Fineline got his Gen II mains and big end bearings. They have arrived. A rebuild thread is on the way.

Camel

[puttputt]

Hi Camel, I am curious to know why you havet 5 broken busa 11 motors in your clean room, are they a bit soft ?

[Maj]

There not soft, i am putting over 300hp through mine,
Camels stuff is in abused 4 wheel vehicles

[fasterfaster]

There not soft, i am putting over 300hp through mine,
Camels stuff is in abused 4 wheel vehicles

Ditto on that Greg .................. Camel tell him to try using a clutch also might help those little doggies
How's things going over there anyways you old flea carrier ?
When you heading North again ?
Cheers Pete

[GRUNTMAX]

Bob Brown, Penny Wong, Paul Keating, Bob Car, .....The Late Freddy Mercury; http://www.youtube.com/watch?v=HDe9Z_Qu8V4

... they are all bent, maybe that's why they invented Heavy Duty Output Shafts; http://www.schnitzracingstore.com/catalo...id=4877082&showprevnext=1

[Fineline22]

[Maj]

Seen the results of not disengaging one gear before selecting the next, not mine thankfully, but it spat the pieces it did not like out through the back .
Think that was probably a selector or shaft flex problem, on a bike...

Cars put a lot more strain everywhere,
worked on one westfield car with busa motor, and had to pull it down for gearbox repairs, race cut all the gears on both drive side and decell , but the thing that stood out most to me was the galling of the casehalves , they had fretted against one another like i had never seen before, put case studs in to try and hold it better , in that circumstance i could see how the middle gears of the set like 3 and 4 could flex the shafts enough to do a lot of damage , and made me carefull just how much load i put on turbo bikes on the dyno in those gears

[Camel]

I think the key indicator is the fact that the shift fork shafts are not bent; they're not in the least bit damaged.

Something to do with gear position wasn't aligned; given that the forks are okay I'm guessing that one causal factor was that the shift fork shafts flexed.

Another may be, as Fineline alluded to, mainshaft flex. This particular engine was hooked up to a R180 Nissan diff via a propshaft with CV joints. The CV closest to the Busa mainshaft (where the sprocket normally sits) is not supported by a bearing. It could be that harmonic dissonance was created in the prop shaft, leading to a whipping effect on the main shaft.

So as short and tough as the main shaft is, there may have been sufficient flex to allow two gears to try and mesh simultaneously when a gear change was attempted. This high torque effect on the cojoined 3-4 drive gears twisted the countershaft.

Actually, the more I think about it, the more the harmonic dissonance theory makes sense. The brinelling (fretting) is more pronounced on the Mainshaft output bearing side than on the clutch side of the countershaft. The engine wasn't running long enough after the incident for that amount of brinelling to occur from the bent countershaft.

Another factor supporting the theory is the state of the shift forks. A logitudinal shunt from a twisted mainshaft would cause the shift fork shafts to flex without necessarily damaging the forks. If anything, the flexible shift fork shafts may have prevented further damage. Is their inclusion an acknowledgement by the Hayabusa engineers that this flex in the main and countershafts exists and that further flexibility, (rather than reinforcement) is a preferred option?

There is no doubting the incredible strength of the Hayabusa gearbox. The torque load on the gears shown above would have shattered a lesser gearbox. Or at the very least stripped a lot of teeth. For teeth to twist and not break like these is testimony to the Hayabusa's toughness.


And as for Pete calling me a flea carrier; you've got a hide you old dog!

I'm actually over your way next week. I'll give you a call.

Camel

[Fineline22]

[Camel]

[Aussie Steve]

A sacrificial joint betwwen the final drive and the drive shaft would be the way to go... snap the connection before it toasts the gearbox??

[whitedragon]

Guys this is my attempt to cushion the blows to the box
by using a rubber coupling
The gear case shaft is fully supported so there's no weight hanging off the output shaft
   

[Camel]

Bloody good idea. Innovative and solves a host of issues. Hyvo chain inside the case? Or roller in an oil bath? (without o/x rings of course).

[whitedragon]

Hy-vo chain Mark just have to finish it all off then go beat up on it and find the next weak link

[Camel]

LOL, give it to Jet, he'll find it!

You running a rocking tensioner in the transfer case? What sort of oil? Got a temp gauge? Where's Peter Falconio?